/* 封装ajax函数
 * @param {string}opt.type http连接的方式，包括POST和GET两种方式
 * @param {string}opt.url 发送请求的url
 * @param {boolean}opt.async 是否为异步请求，true为异步的，false为同步的
 * @param {object}opt.data 发送的参数，格式为对象类型
 * @param {function}opt.success ajax发送并接收成功调用的回调函数
 */

function ajax(opt) {
  opt = opt || {};
  opt.method = opt.method.toUpperCase() || 'POST';
  opt.url = opt.url || '';
  opt.async = opt.async || false;
  opt.header = opt.header || {};
  opt.data = opt.data || null;
  opt.success = opt.success || function () {};
  opt.fail = opt.fail || function () {};
  var timeout;
  var xmlHttp = null;
  if (XMLHttpRequest) {
    xmlHttp = new XMLHttpRequest();
  }
  else {
    xmlHttp = new ActiveXObject('Microsoft.XMLHTTP');
  }

  if(opt.async){
    xmlHttp.timeout = 3000;
    xmlHttp.ontimeout = function(event){
      console.log('请求超时！');
    }
  }else {
    //同步超时设置
    timeout = setTimeout( function () {
      xmlHttp.abort();
      clearTimeout(timeout);
      opt.fail('请求超时');
    }, 3*1000 );
  }

  xmlHttp.onload = function () {
    clearTimeout(timeout);
    var result = Object.prototype.toString.call(xmlHttp.responseText) == '[object String]' ? JSON.parse(xmlHttp.responseText) : xmlHttp.responseText;
    if (xmlHttp.readyState == 4 && xmlHttp.status == 200) {
      opt.success(result);
    }else {
      opt.fail(result);
    }
  };

  var params = [];

  for (var key in opt.data){
    params.push(key + '=' + opt.data[key]);
  }
  var postData = params.join('&');

  if (opt.method.toUpperCase() === 'POST') {
    xmlHttp.open(opt.method, opt.url, opt.async);
    for (var key in opt.header){
      xmlHttp.setRequestHeader(key, opt.data[key]);
    }
    xmlHttp.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded;charset=utf-8');
    xmlHttp.send(postData);
  }
  else if (opt.method.toUpperCase() === 'GET') {
    xmlHttp.open(opt.method, opt.url + '?' + postData, opt.async);
    for (var key in opt.header){
      xmlHttp.setRequestHeader(key, opt.data[key]);
    }
    xmlHttp.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded;charset=utf-8');
    xmlHttp.send(null);
  }

}

/*ajax({
      method: 'POST',
      url: 'test.php',
      data: {
        name1: 'value1',
        name2: 'value2'
      },
      header:{},
    success: function (response) {
      console.log(response)
    },
    fail: function (response) {
      console.log(response)
    }
    });*/

export { ajax }

